The value of screening plant extracts to the U.S. pharmaceutical industry is the promise of finding patentable compounds to treat human diseases. Ethnobotanical rationale for selecting targeted plants allows a focused approach in finding compounds of pharmaceutical interest The Phytochemistry Section of "Peruvian Medicinal Plants As Sources Of New Pharmaceuticals" provides the natural products chemistry support for isolating and identifying compounds with antiinfective and antiinflammation activity. These active compounds could provide a starting point for medicinal chemistry programs as well as validating the targets used for screening. Extraction procedures are described that reduce the hit rate resulting from non-specific interactions (e.g. tannins, polyphenolics etc.) so that the program can focus on finding new chemistry or new activities for known compounds. Isolation procedures include the use of scouting columns to determine optimal separation methodology, e.g., C18 HPLC or ion exchange chromatography. Bioassay- guided fractionation is then used to isolate the compound(s) responsible for the extracts activity. Dereplication techniques will play a major role in determining known active compounds. Databases such as "Handbook of Antibiotic Compounds" (Berdy database) and CAS Online are used to dereplicate known compounds with minimal information. Structure determination on low microgram quantities of pure material can be completed using modem spectroscopic techniques including electrospray mass spectrometry and inverse-detected microprobe NMR.